(3) Brush spring tension is incorrect.
ence can be recognized by a roaring or whining noise
that varies in pitch with the speed of the engine.
Oil or carbon particles collect around
18-4. Body Noises.
(5) Commutator is worn out-of-round.
a. Causes. Body noises are produced by loose
screws and bolts that allow various parts of the body to
Generator is loaded in excess of rated
chafe against each other. This chafing produces static
discharges that are a source of interference to radio
receivers. Static charges caused by friction and induced
Commutator segments are burned or
charges from wiring on the vehicles are collected by the
vehicle body. These charges are retained by poorly
grounded sections of the body until they build up to a
(8) There is high insulation between segments
sufficient value to jump to any well-grounded part of the
vehicle. Each discharge causes a spark of sufficient
intensity to create interference in a radio receiver. These
b. Recognition. Sparking between the brushes and
effects are produced only when the vehicle is in motion,
commutator segments may cause interference in nearby
or for a very short period after the vehicle is stopped.
radio sets. This type of interfer-
Figure 18-1. Typical Battery Ignition System